This invention relates to novel .beta.-isocyanato silanes and methods for their synthesis, including methods for preparing novel oxazolidinone intermediate compounds.
Compounds containing isocyanate functional groups are widely used as crosslinking agents in various chemical reaction because of the extremely reactive nature of the isocyanate radical. For example, isocyanate compounds may be reacted with polyols to produce a wide variety of useful polyurethane compositions. Isocyanate compounds are also widely used to crosslink polyethers and polyesters in the manufacture of elastomers and resins. Where such isocyanate compounds also contain silane functional groups, they can be utilized to produce silicone polymeric products.
The commercial preparation of compounds containing an isocyanate functionality is carried out almost exclusively through the reaction of amines with phosgene gas. See, for example, Holtschmidt et al, U.S. Pat. No. 3,178,391, which uses a phosgenation reaction to produce silane-containing isocyanates and Pepe, U.S. Pat. No. 3,584,024, which also utilizes a phosgene reactant to produce isocyanato-substituted siloxanes.
However, the use of phosgene presents many manufacturing difficulties because of its toxicity and the handling problems it entails. Additionally, the reaction conditions utilized restrict, somewhat, the types of isocyanate compounds which may be produced.
Others have developed procedures for producing isocyanate compounds which avoid the use of phosgene as a reactant. For example, Speier, U.S. Pat. No. 3,170,891, teaches a method which involves reacting a silane with an acyl chloride and then decomposing the intermediate product to produce an isocyanato silane. Hedaya et al, U.S. Pat. No. 4,064,151, teach reacting amine starting materials with carbon dioxide in a triethylamine solvent to produce a carbamic acid salt. The carbamic acid salt is then reacted with a halosilane and the reaction product pyrolyzed to form a halosilyl isocyanate.
However, the need still exists in the art for a relatively simple procedure for producing isocyanato silanes which avoids the use of phosgene and which forms monomeric reactants which are useful in producing a wide range of polyurethane and silicone polymers.